Archived: Frequently Asked Questions for Emona ETT-202 DATEx: Part 2

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Contents

Describe the DATEx system hardware?

The DATEx is comprised of a set of independent circuit blocks and a set of NI ELVIS blocks for access to NI ELVIS functionality. More specifically:

  • 23 DATEx circuit blocks
  • 4 NI ELVIS blocks
    • An "DIGITAL I/O" input/output blocks with:
      • 4 digital inputs
      • 4 digital outputs
    • A "ANALOG I/O" input/output block with:
      • 2 ADC inputs connected to the NI ELVIS, for use with the NI ELVIS BODE ANALYZER or custom use
      • 2 DAC outputs connected to the NI ELVIS, for use with the NI ELVIS ARB or for custom usage.
    • A "FUNCTION GENERATOR" block with:
      • A “FUNC OUT” output to apply a generated signal
      • A “SYNC” output for synchronization pulses
      • A “VCO IN” input to apply FM modulation to the generated signal
    • An "VARIABLE DC" block with:
      •  2 outputs from the NI ELVIS VARIABLE POWER SUPPLY signals

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What equipment do I need to use the DATEx?

The DATEx is intended as a complete, stand-alone telecommunications training board when plugged into an NI ELVIS unit. The DATEx unit will not work without an NI ELVIS.

The NI ELVIS provides the necessary measurement equipment for conducting DATEx experiments.

The DATEx comes complete with the patch cords, scope leads, headphones, CD-ROM with DATEx Soft Front Panel VI and VIs for each DATEx block, User Manual and Experiment Manual.

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How many experiments can you do with the DATEx? What kind of experiments can the DATEx do?

Because the DATEx models mathematical systems using functional building blocks, the number and type of experiments is very broad.

The DATEx can implement over 30 experiments covering both analog & digital telecommunications topics, from modelling basic mathematical equations, all the way through to spread spectrum modulation.

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What can I do if I don't have enough blocks to make the experiment I'm interested in?

  • Consider implementing that function in LabVIEW. To do so, you can employ connections found on the DIGITAL I/O, FUNCTION GENERATOR, ANALOG I/O and/or the VARIABLE DC blocks to access the appropriate signals from your LabVIEW applications.
  • Consider splitting the task and distribute onto two DATEx/NI ELVIS units sitting side by side. You should link the GND points of each DATEx unit for best signal integrity.

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How do you "model" a telecommunications "channel"?

A "channel" is the path or medium along which the modulated or coded message is transmitted. eg. radio waves, coaxial cable, telephone line, etc. In telecommunications, the characteristics of a "channel" must be known and measured, in order to ensure the message is correctly transferred from transmitter to receiver.

There are three important "channel" characteristics:

  • signal amplitude attenuations and distortion.
  • signal phase delay and distortion.
  • noise which is added to the signal.

DATEx includes a selection of filter blocks which can be used to model the channel's amplitude and phase characteristics. "Channel" noise is modelled using a NOISE GENERATOR block and added using an ADDER block. This effectively models an AWGN channel.

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How do I learn how to put together experiments - where can I get some ideas?

Ideas for block diagrams are available from many sources including:

  • Communications textbooks, magazines and research papers;
  • The user's own new ideas and theories;
  • The DATEx Experiment Manual;

Additionally, all of the LabVIEW resources related to telecommunications.

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Isn't the DATEx just a simple "demonstration" system?

No.  A "demonstration" system is typically one box, which only outputs demonstration waveforms (eg: AM and DSB envelopes, or TDM sampled signals, etc.) The user has no real control over themethod of implementation of each experiment, other than a few gain controls.

The DATEx is a true "modelling" system. No one block has an isolated function - blocks are used together to build-up systems.

The DATEx does not include, for example, an "AM modulator" block, or an "SSB demodulator" block. These functions are patched together using independent Adder blocks, Multiplier blocks, Signal Source blocks, and so on.

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What is the MASTER SIGNALS block?

MASTER SIGNALS block provides the user with a set of synchronized carrier, sampling and message signals. These synchronized signals will provide the student with clear and stable textbook-like waveforms, which will aid the student's understanding of the theory.

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Why is it important that the MASTER SIGNALS outputs are synchronised?

Using synchronized signals in experiments will allow the user to view stable, text book-like waveforms on the NI ELVIS oscilloscope.

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Why is the DATEx "carrier" only 100kHz, when real telecommunications systems often use carrier frequencies ranging from 1MHz to many Giga Hertz?

The DATEx is a mathematical, telecommunications theory and signal processing modelling system. DATEx models the mathematics. The DATEx does not consider high frequency circuit applications because this is a separate and very specialized area of Electronics Circuit Theory.

For example, a student can model and take detailed measurements of a complete BPSK (binary phase shift keying) link. The mathematical equations behind the theory of such a satellite link will work both at 100kHz and at 10GHz. Only the circuits are different. In the DATEx, the carrier frequency has simply been scaled down to 100kHz.

The benefits of this modeling approach are:

  • the carrier is visible within the modulated signal on the NI ELVIS scope;
  • simple patching leads can be used rather than coaxial cables and BNC terminals;

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Additional Resources

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